The present invention relates to a method of making a compensator for a liquid crystal display device and more particularly to a method of making a compensator for a liquid crystal device which is intended to improve the display quality, for example, prevent the coloration of liquid crystal display, or enlarge the viewing angle characteristic.
Liquid crystal display occupies an important position in the display field because of such characteristics thereof as being driven at a low voltage, light weight and low cost. For example, a super-twisted nematic (hereinafter referred to simply as "STN") liquid crystal display of a simple matrix driving type permits a large screen display based on a multiplex driving dot matrix system and has such characteristics as being high in contrast and wide in viewing angle as compared with the conventional twisted nematic (TN) type liquid crystal display. Because of these characteristics, the STN liquid crystal display is widely used in the field of liquid crystal displays requiring a large screen display such as personal computers, word processors and various data terminals. However, since the STN method utilizes a birefringence effect, the coloration in yellow or blue has been unavoidable. The display in such a colored mode is seriously disadvantageous in that not only it is undesirable on the user side but also cannot realize a desired color display.
Also in the case of a liquid crystal display using a thin film transistor (simply "TFT" hereinafter) which is a typical example of an active matrix driving type, there arises a serious drawback of the same coloration as that mentioned above when the cell gap is made smaller for the purpose of improving the response speed and the viewing angle characteristic.
Further, both such simple matrix type and active matrix type are disadvantageous in that a viewing angle range permitting a satisfactory image is limited, which is peculiar to the liquid crystal display.
As an optical element for overcoming such drawbacks of the liquid crystal display, the present inventors have previously proposed a compensator for a liquid crystal display constituted by a liquid crystalline polymer with a twisted nematic structure fixed (Japanese Patent Laid Open No. 87720/1991). Further, as a simpler manufacturing method high in mass productivity for such liquid crystal display compensator, the present inventors have also proposed a manufacturing method in which a liquid crystalline polymer layer formed on an orientating substrate is transferred onto light transmitting substrate (Japanese Patent Laid Open No. JP4-57017A).
Such optical element is required to have a high degree of uniformity in its film thickness in all area of the compensator. In other words, it is required that there be little unevenness in the film thickness in all area of the compensator. Also in the above manufacturing method proposed by the present inventors, the attainment of a high degree of uniformity remains as an important subject to be achieved in practising the method on an industrial scale.
It is the object of the present invention to provide a method of making a compensator for a liquid crystal display device, comprising transferring a liquid crystalline polymer layer formed on an orientating substrate onto a light transmitting substrate, which method can attain a high degree of uniformity in film thickness.